1. Field of the Invention
The present invention relates to a line transducer for a transmission line used in the microwave band and the millimeter wave band, and a high-frequency component, module, and communication apparatus incorporating the same.
2. Description of the Related Art
A high-frequency package incorporating a line transducer in which a substrate with a transmission line formed thereon is coupled with a waveguide is disclosed in Japanese Unexamined Patent Application Publication No. 11-112209.
In the line transducer, a transmission line is formed on one surface of a dielectric substrate, one end thereof being terminated and the other end thereof being connected to a high-frequency element. On the other surface of the dielectric surface, a ground electrode (ground layer), having an opening formed in a region opposite to the terminated end, is formed. On a surface including the opening, a matching dielectric member is formed. A waveguide is electrically connected to the surface on which the ground electrode is formed so that the waveguide is centered at the opening, whereby the transmission line and the waveguide are connected to each other.
Furthermore, on the surface with the ground electrode, a second dielectric substrate provided with the matching dielectric member is laminated. On the surface of the second dielectric substrate, a conductor member is formed, and via holes or through holes connecting the conductor member and the ground electrode are formed so that the waveguide and the ground electrode are connected to each other, whereby the transmission line and the waveguide are connected to each other.
The high-frequency line transducer according to the related art, however, has had the following problems to be overcome.
In the line transducer according to the related art, the ground electrode of the transmission line and the conductor member of the waveguide must be properly connected, and an inadequate connection causes connection loss. Furthermore, when the connection is formed using a brazing alloy or the like, extrusion, insufficiency, etc. of the brazing alloy affects electrical characteristics to such an extent as to inhibit stable connection, making management of connection process difficult. This increases the amount of work required, thereby resulting in increased cost. Furthermore, when temperature changes at the connection, for example, by a thermal shock, cracking occurs at the connection, thereby considerably changing electrical characteristics. When the connection is formed using a screw, electrical characteristics are considerably affected by precision of screwing, and electrical characteristics could be degraded due to a gap or contact resistance associated with the screw.